function openPopup (imageURL, caption) {

/*
This routine creates a pop-up window, and ensures that it takes focus. It is 
intended to be called from an anchor tag. The new window will resize itself to 
the optimum size, so we make it as large as the largest required window to
overcome bugs in various manifestations of various browsers.
  
Author:   John Gardner
Written:  8th November 2003
Updated:  27th January 2004

Calling sequence: <a href="a.jpg" onClick="return openPopup('a.jpg','Caption');">

The first parameter is the URL of the image to be opened, and the second 
parameter is the caption for the image which is displayed in the window title
and in the alt property of the image tag.

Note that the calling sequence will simply open the image in the main window if
JavaScript isn't enabled.
  
*/

  // Constants - change these to suit your requirements Note that the defaultWidth
  // and defaultHeight variables should be set to more than your largest image to
  // overcome a bug in Mozilla (at least up to Firefox 0.9).

  var windowTop = 10;                // Top position of popup
  var windowLeft = 10;                // Left position of popup
  var defaultWidth = 550;             // Default width (for browsers that cannot resize)
  var defaultHeight = 400;            // Default height (for browsers that cannot resize)
  var onLoseFocusExit = false;         // Set if window to exit when it loses focus
  var undefined;

  // Set up the window open options
  var Options = "width=" + defaultWidth + ",height=" + defaultHeight + ",top=" + windowTop + ",left=" + windowLeft + ",resizable" 
  
  // Now write the HTML markup to the new window, ensuring that we insert the 
  // parameter URL of the image and the parameter description of the image in 
  // the right place.
  var myScript = "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">\n" +
    "<html>\n" + 
    "<head>\n" + 
    "<title>" + caption + "\</title>\n" +
    "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=ISO-8859-1\">\n" +
    "<meta http-equiv=\"Content-Language\" content=\"en-gb\">\n" +
    "<script language=\"JavaScript\" type=\"text/javascript\">\n" +
    "function resizewindow () {\n" +
    "  var width = document.myimage.width;\n" + 
    "  var height = document.myimage.height;\n";
  
  // Netscape  
  if (navigator.appName.indexOf("Netscape") != -1) { 
    myScript = myScript +  "  window.innerHeight = height;\n  window.innerWidth = width;\n"
  }
   
  // Opera 
  else if (navigator.appName.indexOf("Opera") != -1) {
    myScript = myScript +  "  window.resizeTo (width+12, height+31);\n"
  }
  
  // Microsoft 
  else if (navigator.appName.indexOf("Microsoft") != -1) { 
    myScript = myScript + "  window.resizeTo (width+12, height+31);\n" 
  }
  
  // Assume a frig factor for any other browsers
  else {
    myScript = myScript + "  window.resizeTo (width+14, height+34);\n"
  }
      
  myScript = myScript + "}\n" + "window.onload = resizewindow;\n" +
    "</script>\n</head>\n" + "<body ";
    
  // If the window is required to close when it loses focus.
  if (onLoseFocusExit) {myScript = myScript + "onblur=\"self.close()\" ";}
    
  myScript = myScript + "style=\"margin: 0px; padding: 0px;\">\n" +
    "<img src=\"" + imageURL + "\" alt=\"" + caption + "\" title=\"" + caption + "\" name=\"myimage\">\n" + 
    "</body>\n" +  "</html>\n";
        
  // Diagnostic - uncomment the next line if you wish to see the script generated.   
  //alert (myScript);
  
  // Create the popup window
  //var imageWindow = window.open ("","imageWin",Options);
  var imageWindow = window.open ("",caption,Options);
  imageWindow.document.write (myScript);
  imageWindow.document.close ();
  if (window.focus) imageWindow.focus();
  return false;
}

